Induced pluripotent stem (iPS) cells have a tremendous potential for aidvancing our understanding of human development and disease. To help unlock this potential we have organized a program to (A) comprehensively identify the genetic and epigenetic components of the regulatory network that maintains cells in a pluripotent state;(B) characterize culture-induced variation in the activites of these components in pluripotent cells;and (C) characterize temporal variation in their activities during induction of pluripotency with defined factors. To achieve these goals, we have formulated four interdependent projects: Project I (Meissner) will (1) characterize transcriptional coregulators and small non-coding RNAs that modulate the activity of the core pluripotency transcription factors, and (2) define and isolate subpopulations from pluripotent cell cultures to characterize their transcriptional and epigenetic states. Project II (Rinn) will characterize long non-coding RNAs expressed in pluripotent cells and elucidate their role in remodeling the epigenetic landscape during reprogramming. Project III (Mikkelsen) will characterize the cis-regulatory modules that direct activation, maintenace and repression of gene expression in pluripotent cells by recruiting transcription factors and their coregulators to key genomic loci. Project IV (Eggan) will characterize the inheritance patterns and maintenance of inactivated X chromosomes during reprogramming and in pluripotent cell cultures. The four projects rely on complementary use of innovative high-throughput genomic and proteomic technologies to profile high-quality iPS cell lines. The integration of data and insights from each of the projects will generate a comprehensive view of protein-protein, protein-RNA and protein-DNA interactions essential to the maintenace of pluripotency (goal A). This intergrated view will then guide studies of culture- induced and temporal variation in the network (goals B and C). PUBLIC HEALTH RELEVANCE: Induced pluripotent stem cells are a potential revolutionary tool for disease modeling, drug screening and regenerative medicine. This program is organized to fully characterize the molecular properties of these cells, which is essential to ensure that their use in biomedicine is effective and safe.